Local Electronic Properties of Graphene on a BN Substrate via Scanning Tunneling Microscopy

Decker, Régis; Wang, Yang; Brar, Victor W.; Regan, William; Tsai, Hsin‐Zon; Wu, Qiong; Gannett, Will; Zettl, A.; Crommie, Michael F.

doi:10.1021/nl2005115

Cited by 561 publications

(639 citation statements)

References 29 publications

Supporting

Mentioning

589

Contrasting

Unclassified

Order By: Relevance

“…The valley current in BLG decreases through intervalley scattering, which requires a large momentum transfer (e.g., by atomic scale disorders). Such disorders are found to be Page 8 of 16 extremely rare in cleaved BLG crystals 19,20 , implying a large valley diffusion length 21,22 . In the present study, an appreciable nonlocal signal was observed in samples up to 10 m long.…”

mentioning

confidence: 99%

See 1 more Smart Citation

Gate-tunable topological valley transport in bilayer graphene

et al. 2015

View full text Add to dashboard Cite

Valley pseudospin, the quantum degree of freedom characterizing the degenerate valleys in energy bands 1 , is a distinct feature of two-dimensional Dirac materials [1][2][3][4][5] . Similar to spin, the valley pseudospin is spanned by a time reversal pair of states, though the two valley pseudospin states transform to each other under spatial inversion. The breaking of inversion symmetry induces various valley-contrasted physical properties; for instance, valley-dependent topological transport is of both scientific and technological interests [2][3][4][5] . Bilayer graphene (BLG) is a unique system whose intrinsic inversion symmetry can be controllably broken by a perpendicular electric field, offering a rare possibility for continuously tunable valley-topological transport. Here, we used a perpendicular gate electric field to break the inversion symmetry in BLG, and a giant nonlocal response was observed as a result of the topological transport of the valley pseudospin. We further showed that the valley transport is fully tunable by external gates, and that the nonlocal signal persists up to room temperature and over long distances. These observations challenge contemporary understanding of topological transport in a gapped system, and the robust topological transport may lead to future valleytronic applications.In crystalline solids, a topological current can be induced by the Berry phase of the electronic wave function 6 . Examples include the quantum Hall current in a magnetic field, and the spin Hall current arising from spin-orbit coupling. Such topological transport is robust against impurities and defects in materials -a feature that is much sought after in potential electronic applications. In such applications, the ability to switch and to continuously tune the topological transport is crucial. The topological current is in principle dictated by the crystal symmetry, which is difficult to change in Page 3 of 16 bulk materials. Bilayer graphene, however, offer new opportunities in which inversion symmetry can be controllably broken by an external electric field in the perpendicular direction.The topological current controlled by the inversion symmetry breaking is associated with carriers' valley pseudospin, which characterises the two-fold degenerate band-edges located at the corners of the hexagonal Brillouin zone. The topological Hall current, odd under time-reversal but even under inversion, is strictly zero in pristine mono-and bi-layer graphene which respect both symmetries. When the inversion symmetry is broken, however, time-reversal symmetry requires the Hall currents to have opposite signs and equal magnitudes in the two valleys (i.e., a valley The nonlocal transport persists up to room temperature and over long distances (up to 10 m). Our results represent major progress in the quest for a robust, tunable valley pseudospin system among various alternatives [3][4][5]11,12 , and indicate the possibility of using the nonlocal topological transport in practical applications under ambient conditio...

show abstract

mentioning

confidence: 99%

“…extremely rare in cleaved BLG crystals 19,20 , implying a large valley diffusion length 21,22 . In the present study, an appreciable nonlocal signal was observed in samples up to 10 m long.…”

mentioning

confidence: 99%

Gate-tunable topological valley transport in bilayer graphene

et al. 2015

View full text Add to dashboard Cite

show abstract

“…Indeed the functional characteristics of graphene on h-BN are drastically improved compared to conventional SiO2 substrates. [10][11][12] Furthermore h-BN allows to tune the band gap of graphene in heterostructures 8,13 or in hybridized single-layer systems 14 . Regarding the use of epitaxial BN monolayers as templates, several recent reports highlight functionalities gained by the decoupling and ordering properties of BN [15][16][17][18][19] .…”

mentioning

confidence: 99%

Boron Nitride on Cu(111): An Electronically Corrugated Monolayer

et al. 2012

View full text Add to dashboard Cite

show abstract

“…The graphene crystal structure can be distinctly imaged in silicone oil at room temperature with a resolution on par with graphene resolved using cryogenic STM (refs 47,48). The hexagonal lattice of carbon atoms can also be resolved at high tunnel-current set points (∼1.8 nA), reflecting the structural stability of the interface between the graphene and the spacer layer, previously observed for graphene on two-dimensional insulating platforms 47 yields a net energy of −4.3 eV nm −2 , indicating a preference of ∼500 meV nm −2 for graphene adsorption on the spacer layer rather than on bare gold. This implies that a single layer of graphene can lie on the spacer layer without disrupting its geometric order (see Supplementary Section 8.6 for binding-energy calculations).…”

Section: Atom-scale Analysis Of Graphene In Silicone Oilmentioning

confidence: 53%

Nanoelectrical analysis of single molecules and atomic-scale materials at the solid/liquid interface

et al. 2014

View full text Add to dashboard Cite

Evaluating the built-in functionality of nanomaterials under practical conditions is central for their proposed integration as active components in next-generation electronics. Low-dimensional materials from single atoms to molecules have been consistently resolved and manipulated under ultrahigh vacuum at low temperatures. At room temperature, atomic-scale imaging has also been performed by probing materials at the solid/liquid interface. We exploit this electrical interface to develop a robust electronic decoupling platform that provides precise information on molecular energy levels recorded using in situ scanning tunnelling microscopy/spectroscopy with high spatial and energy resolution in a high-density liquid environment. Our experimental findings, supported by ab initio electronic structure calculations and atomic-scale molecular dynamics simulations, reveal direct mapping of single-molecule structure and resonance states at the solid/liquid interface. We further extend this approach to resolve the electronic structure of graphene monolayers at atomic length scales under standard room-temperature operating conditions.T he elemental properties of carbon nanostructures are environment dependent. Interpreting the synergism between electronically active nanomaterials and their local chemical domain is pivotal to both scientific and technological interests. Scanning probe microscopy operated at cryogenic conditions with functionalized metal tips 1,2 in combination with inorganic decoupling platforms 3,4 is a widely adopted technique to examine the intramolecular structure of organic materials. In addition to probing matter under ultrahigh-vacuum conditions, scanning tunnelling microscopy (STM) operated at the solid/liquid interface 5-11 has previously been demonstrated to record real-time molecular dynamics 7,12-14 , register ultrafast chemical reactions 8,15 , probe the structure of supra-molecular architectures [16][17][18] and chemical-fieldeffect transistors 19 , and perform spectral analysis of molecules 6,13,20 and real-space visualization of biomolecules 5 at room temperature. It would be highly attractive to capitalize on principal findings from these two research disciplines to probe the precise electronic states in liquids and quantitatively describe the functionality of single molecules and two-dimensional nanostructures. The experimental challenge lies in addressing the electrochemical congestion present at the solid/liquid electrical interface at room temperature, which stems from the high mobility of organic molecules on metals, the dynamics of the solvent that serves as a liquid sheath and the detrimental effects of the metallic platform due to mixing of metal bands with discrete molecular electronic states 21 . A potential strategy is to employ nonpolar, highly viscous liquid sheaths with low affinity towards the substrate and to engineer a spacer layer 3,22,23 that electrically disconnects the organic material of interest from metal-induced perturbations. The bottom-up construction of the spac...

show abstract

Local Electronic Properties of Graphene on a BN Substrate via Scanning Tunneling Microscopy

Cited by 561 publications

References 29 publications

Gate-tunable topological valley transport in bilayer graphene

Gate-tunable topological valley transport in bilayer graphene

Boron Nitride on Cu(111): An Electronically Corrugated Monolayer

Nanoelectrical analysis of single molecules and atomic-scale materials at the solid/liquid interface

Contact Info

Product

Resources

About